Lidl received praise for its Salmon Wellington with Spinach Cream and Deluxe Smoked Scottish Salmon Selection.

Waitrose has responded to the threat by rethinking the role of a supermarket. This has involved opening wine bars, sushi bars and even upmarket restaurants.

The chain is also focussing on the provenance of its fresh food all the way to the farm and fishing boats.

Its sales were up by £214m over the 12 weeks compared to a year ago, which continues a record of growth dating back to March 2009 and allowed it to maintain its market share.

The sales figures come from Kantar Worldpanel. Its head of retailer and consumer insight, Fraser McKevitt, said: ‘Ten million households visited Lidl’s expanding network of stores during the past 12 weeks, with alcohol and fresh produce performing particularly well.

‘Lidl is growing sales 40per cent faster with families than with households without children. Families tend to buy more items each time they shop, so strong growth with this demographic has helped Lidl to increase its average basket size year on year.

‘Not far behind, Aldi grew sales by 17.2per cent, attracting 1.1 million more shoppers through its doors than this time last year and increasing market share by 0.8 percentage points to stand at 7per cent.’

Kantar said shop price inflation has increased slightly in recent months to 3.3per cent a year.

Mr McKevitt said: ‘At the current rate, price increases could add a further £138 to the average household’s annual grocery bill, with the price of butter and fish most affected.’

Separate research from retail analysts Nielsen found the number of people making cuts to household spending has hit its highest level for two years.

Over half of Britons – 53per cent – admitted to taking cost-cutting measures in the second quarter of this year.

Nielsen’s UK head of retailer and business insight, Mike Watkins, said: ‘The return of inflation and rising concerns about the economy mean the weekly grocery shop is now the most popular target for people to cut down on household expenses.